scholarly journals Stability order of isomeric benzenoid hydrocarbons and Kekulé structure count

2009 ◽  
Vol 74 (2) ◽  
pp. 155-158 ◽  
Author(s):  
Slavko Radenkovic ◽  
Ivan Gutman
Keyword(s):  
Electron Energy ◽  
Thermodynamic Stability ◽  
Anomalous Behavior ◽  
Kekulé Structure ◽  
Benzenoid Hydrocarbons ◽  
Total Electron ◽  
Total Electron Energy ◽  
Structure Count ◽  
Resonance Energies ◽  
Stability Order

The commonly accepted opinion that the thermodynamic stability of isomeric benzenoid hydrocarbons (assessed by their total ?-electron energy and various resonance energies) increases with increasing number of Kekul? structures is shown to be violated in numerous cases. The smallest examples of such anomalous behavior are two hexacyclic pericondensed benzenoids of formula C24H14 and several pairs of heptacyclic catacondensed benzenoids of formula C30H18.

scholarly journals Iterative estimation of total π-electron energy

2005 ◽  
Vol 70 (10) ◽  
pp. 1193-1197 ◽  
Author(s):  
Lemi Türker ◽  
Ivan Gutman
Keyword(s):  
Lower Bound ◽  
Electron Energy ◽  
Upper Bound ◽  
Upper Bounds ◽  
Lower And Upper Bounds ◽  
Benzenoid Hydrocarbons ◽  
Total Electron ◽  
Iterative Estimation ◽  
Total Electron Energy ◽  
Almost All

In this work, the lower and upper bounds for total ?-electron energy (E) was studied. A method is presented, by means of which, starting with a lower bound EL and an upper bound EU for E, a sequence of auxiliary quantities E0 E1, E2,? is computed, such that E0 = EL, E0 < E1 < E2 < ?, and E = EU. Therefore, an integer k exists, such that Ek E < Ek+1. If the estimates EL and EU are of the McClelland type, then k is called the McClelland number. For almost all benzenoid hydrocarbons, k = 3.

scholarly journals The Hall rule in fluoranthene-type benzenoid hydrocarbons

2008 ◽  
Vol 73 (10) ◽  
pp. 989-995 ◽  
Author(s):  
Jelena Djurdjevic ◽  
Slavko Radenkovic ◽  
Ivan Gutman
Keyword(s):  
Electron Energy ◽  
Linear Relation ◽  
Fixed Number ◽  
Numerical Results ◽  
Benzenoid Hydrocarbons ◽  
Total Electron ◽  
Total Electron Energy

The applicability of the Hall rule (linear relation between the total ?-electron energy and the number of Kekul? structures) was investigated in the case of fluoranthene-type benzenoid hydrocarbons. It was found that the originnal Hall rule is not obeyed, but holds for sets of isomers with a fixed number of bay regions. For such groups of isomers, two apparently contradictory Hall-type rules were conceived, and it was found that both give almost identical numerical results.

scholarly journals On a class of approximate formulas for total ח-electron energy of benzenoid hydrocarbons

2001 ◽  
Vol 66 (2) ◽  
pp. 101-106 ◽  
Author(s):  
Ivan Gutman ◽  
Tanja Soldatovic
Keyword(s):  
Electron Energy ◽  
Benzenoid Hydrocarbons ◽  
Spectral Moments ◽  
Total Electron ◽  
Total Electron Energy ◽  
Approximate Formulas

The method for obtaining approximate formulas of the (n, m)-type for the total -electron energy of benzenoid hydrocarbons (communicated in J. Serb. Chem. Soc. 54 (1989) 189) is simplified and extended so as to include arbitrary spectral moments. The accuracy of the formulas thus obtained is very good and these need no additional fitting by means of empirically determined parameters.

scholarly journals Dependence of the total -electron energy on large number of non-bonding molecular orbitals

2004 ◽  
Vol 69 (10) ◽  
pp. 777-782 ◽  
Author(s):  
Ivan Gutman ◽  
Dragan Stevanovic ◽  
Slavko Radenkovic ◽  
Svetlana Milosavljevic ◽  
Natasa Cmiljanovic
Keyword(s):  
Electron Energy ◽  
Molecular Orbitals ◽  
Total Electron ◽  
Total Electron Energy

Using a recently developed method for computing the effect of non-bonding molecular orbitals (NBMOs) on the total ?-electron energy (E), it was found that the dependence of E on the number n0 of NBMOs is almost perfectly linear. We now show that this regularity remains valid for very large values of n0, in particular, to hold up to n0 = 20.

A topological index for the total?-electron energy

1975 ◽  
Vol 38 (1) ◽  
pp. 37-47 ◽  
Author(s):  
Haruo Hosoya ◽  
Kikuko Hosoi ◽  
Ivan Gutman
Keyword(s):  
Electron Energy ◽  
Topological Index ◽  
Total Electron ◽  
Total Electron Energy
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